Re: [PATCH v5 17/19] SecurityPkg: Add EncryptionVariable lib with AES

["Wang, Jian J" <jian.j.wang@intel.com>]

Judah,

Just some typos found. See inline comments below starting with "[JianJW]".
With them addressed,

    Reviewed-by: Jian J Wang <jian.j.wang@intel.com>

Regards,
Jian

> -----Original Message-----
> From: Vang, Judah <judah.vang@intel.com>
> Sent: Sunday, November 06, 2022 3:35 PM
> To: devel@edk2.groups.io
> Cc: Wang, Jian J <jian.j.wang@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>;
> Xu, Min M <min.m.xu@intel.com>; Mistry, Nishant C
> <nishant.c.mistry@intel.com>
> Subject: [PATCH v5 17/19] SecurityPkg: Add EncryptionVariable lib with AES
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2594
> 
> V3: Change AllocateZeroPool() with AllocatePages() and FreePool()
> with FreePages(). FreePool() is not supported in PEI phase so this was
> causing a memory leak. Reverse the order of the FreePages() call.
> 
> V1: Add encryption/decryption of protected variable functionality.
> Add functions to get/set cipher data of a protected variable.
> This is use for supporting confidentiality for protected
> variables.
> 
> Cc: Jian J Wang <jian.j.wang@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Nishant C Mistry <nishant.c.mistry@intel.com>
> Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
> Signed-off-by: Nishant C Mistry <nishant.c.mistry@intel.com>
> Signed-off-by: Judah Vang <judah.vang@intel.com>
> ---
>  SecurityPkg/Library/EncryptionVariableLib/EncryptionVariableLib.inf |  43 ++
>  SecurityPkg/Library/EncryptionVariableLib/EncryptionVariable.h      |  49 ++
>  SecurityPkg/Library/EncryptionVariableLib/EncryptionVariable.c      | 734
> ++++++++++++++++++++
>  3 files changed, 826 insertions(+)
> 
> diff --git a/SecurityPkg/Library/EncryptionVariableLib/EncryptionVariableLib.inf
> b/SecurityPkg/Library/EncryptionVariableLib/EncryptionVariableLib.inf
> new file mode 100644
> index 000000000000..7ece52f2fb58
> --- /dev/null
> +++ b/SecurityPkg/Library/EncryptionVariableLib/EncryptionVariableLib.inf
> @@ -0,0 +1,43 @@
> +## @file
> +#  Provides variable encryption/decryption services.
> +#
> +#  Copyright (c) 2022, Intel Corporation. All rights reserved.<BR>
> +#
> +#  SPDX-License-Identifier: BSD-2-Clause-Patent
> +#
> +##
> +
> +[Defines]
> +  INF_VERSION                    = 0x00010029
> +  BASE_NAME                      = EncryptionVariableLib
> +  FILE_GUID                      = 459E2CB0-AF4B-4415-B6A1-335E71FD8B85
> +  MODULE_TYPE                    = BASE
> +  VERSION_STRING                 = 1.0
> +  LIBRARY_CLASS                  = EncryptionVariableLib
> +
> +#
> +# The following information is for reference only and not required by the build
> tools.
> +#
> +#  VALID_ARCHITECTURES           = IA32 X64
> +#
> +
> +[Sources]
> +  EncryptionVariable.c
> +  EncryptionVariable.h
> +
> +[Packages]
> +  MdePkg/MdePkg.dec
> +  MdeModulePkg/MdeModulePkg.dec
> +  SecurityPkg/SecurityPkg.dec
> +  CryptoPkg/CryptoPkg.dec
> +
> +[LibraryClasses]
> +  BaseLib
> +  BaseMemoryLib
> +  DebugLib
> +  MemoryAllocationLib
> +  BaseCryptLib
> +
> +[Guids]
> +  gEfiVariableGuid
> +  gEfiAuthenticatedVariableGuid
> diff --git a/SecurityPkg/Library/EncryptionVariableLib/EncryptionVariable.h
> b/SecurityPkg/Library/EncryptionVariableLib/EncryptionVariable.h
> new file mode 100644
> index 000000000000..f35f9f9e3ad7
> --- /dev/null
> +++ b/SecurityPkg/Library/EncryptionVariableLib/EncryptionVariable.h
> @@ -0,0 +1,49 @@
> +/** @file
> +  Definitions used by this library implementation.
> +
> +Copyright (c) 2022, Intel Corporation. All rights reserved.<BR>
> +SPDX-License-Identifier: BSD-2-Clause-Patent
> +
> +**/
> +
> +#ifndef ENCRYPTION_VARIABLE_H_
> +#define ENCRYPTION_VARIABLE_H_
> +
> +#define ENC_KEY_SEP        L":"
> +#define ENC_KEY_SEP_SIZE   2
> +#define ENC_KEY_NAME       L"VAR_ENC_KEY"
> +#define ENC_KEY_NAME_SIZE  22
> +
> +#define ENC_KEY_SIZE    (256/8)
> +#define ENC_BLOCK_SIZE  AES_BLOCK_SIZE
> +#define ENC_IVEC_SIZE   ENC_BLOCK_SIZE
> +
> +#define ENC_PADDING_BYTE  0x0F
> +
> +//
> +// PKCS#5 padding
> +//
> +// #define AES_CIPHER_DATA_SIZE(PlainDataSize)
> +//  (AES_BLOCK_SIZE + (PlainDataSize)) & (~(AES_BLOCK_SIZE - 1))
> +//
> +#define AES_CIPHER_DATA_SIZE(PlainDataSize)  ALIGN_VALUE (PlainDataSize,
> AES_BLOCK_SIZE)
> +
> +#define FREE_POOL(Address)      \
> +    if ((Address) != NULL) {    \
> +      FreePool (Address);       \
> +      (Address) = NULL;         \
> +    }
> +
> +#pragma pack(1)
> +
> +typedef struct {
> +  UINT32    DataType;         // SYM_TYPE_AES
> +  UINT32    HeaderSize;       // sizeof(VARIABLE_ENCRYPTION_HEADER)
> +  UINT32    PlainDataSize;    // Plain data size
> +  UINT32    CipherDataSize;   // Cipher data size
> +  UINT8     KeyIvec[ENC_IVEC_SIZE];
> +} VARIABLE_ENCRYPTION_HEADER;
> +
> +#pragma pack()
> +
> +#endif // _ENCRYPTION_VARIABLE_H_
> diff --git a/SecurityPkg/Library/EncryptionVariableLib/EncryptionVariable.c
> b/SecurityPkg/Library/EncryptionVariableLib/EncryptionVariable.c
> new file mode 100644
> index 000000000000..d128b32f93e0
> --- /dev/null
> +++ b/SecurityPkg/Library/EncryptionVariableLib/EncryptionVariable.c
> @@ -0,0 +1,734 @@
> +/** @file
> +  Implementation of EncryptionVariableLib with AES algorithm support.
> +
> +Copyright (c) 2022, Intel Corporation. All rights reserved.<BR>
> +SPDX-License-Identifier: BSD-2-Clause-Patent
> +
> +**/
> +
> +#include <Uefi.h>
> +
> +#include <Guid/VariableFormat.h>
> +#include <Library/EncryptionVariableLib.h>
> +#include <Library/BaseCryptLib.h>
> +#include <Library/MemoryAllocationLib.h>
> +#include <Library/BaseMemoryLib.h>
> +#include <Library/DebugLib.h>
> +
> +#include "EncryptionVariable.h"
> +
> +/**
> +  Derive encryption key for given variable from variable root key.
> +
> +  The derivation algorithm is depicted below
> +
> +    HKDF_Expand(SHA256, RootKey,
> Name||':'||Guid||':'||Attr||"VAR_ENC_KEY")
> +
> +  @param[in]    VarEncInfo    Pointer to structure containing detailed
> +                              information about a variable.
> +  @param[in]    EncKeySize    Size of key requested.
> +  @param[out]   EncKey        Buffer of key.
> +
> +  @retval TRUE    The key was derived successfully.
> +  @retval FALSE   Failed to generate encryption key.
> +
> +**/
> +STATIC
> +BOOLEAN
> +EncVarLibGenEncKey (
> +  IN VARIABLE_ENCRYPTION_INFO  *VarEncInfo,
> +  IN UINTN                     EncKeySize,
> +  OUT UINT8                    *EncKey
> +  )
> +{
> +  BOOLEAN  Status;
> +
> +  struct {
> +    VOID     *Data;
> +    UINTN    Size;
> +  }                 InfoGroup[6];
> +  UINT8  *Info;
> +  UINTN  InfoSize;
> +  UINTN  Index;
> +  UINT8  Salt[16];
> +
> +  //
> +  // info: Name||':'||Guid||':'||Attr||"VAR_ENC_KEY"
> +  //
> +  InfoGroup[0].Size = VarEncInfo->Header.NameSize;
> +  InfoGroup[0].Data = VarEncInfo->Header.VariableName;
> +
> +  InfoGroup[1].Size = ENC_KEY_SEP_SIZE;
> +  InfoGroup[1].Data = ENC_KEY_SEP;
> +
> +  InfoGroup[2].Size = sizeof (*VarEncInfo->Header.VendorGuid);
> +  InfoGroup[2].Data = VarEncInfo->Header.VendorGuid;
> +
> +  InfoGroup[3].Size = ENC_KEY_SEP_SIZE;
> +  InfoGroup[3].Data = ENC_KEY_SEP;
> +
> +  InfoGroup[4].Size = sizeof (VarEncInfo->Header.Attributes);
> +  InfoGroup[4].Data = &VarEncInfo->Header.Attributes;
> +
> +  InfoGroup[5].Size = ENC_KEY_NAME_SIZE;
> +  InfoGroup[5].Data = ENC_KEY_NAME;
> +
> +  for (InfoSize = 0, Index = 0; Index < ARRAY_SIZE (InfoGroup); ++Index) {
> +    InfoSize += InfoGroup[Index].Size;
> +  }
> +
> +  Info = AllocatePages (EFI_SIZE_TO_PAGES (InfoSize));
> +  if (Info == NULL) {
> +    ASSERT (Info != NULL);
> +    return FALSE;
> +  }
> +
> +  for (InfoSize = 0, Index = 0; Index < ARRAY_SIZE (InfoGroup); ++Index) {
> +    CopyMem (Info + InfoSize, InfoGroup[Index].Data, InfoGroup[Index].Size);
> +    InfoSize += InfoGroup[Index].Size;
> +  }
> +
> +  Status = HkdfSha256ExtractAndExpand (
> +             VarEncInfo->Key,
> +             VarEncInfo->KeySize,
> +             Salt,
> +             0,
> +             Info,
> +             InfoSize,
> +             EncKey,
> +             EncKeySize
> +             );
> +
> +  FreePages (Info, EFI_SIZE_TO_PAGES (InfoSize));
> +
> +  return Status;
> +}
> +
> +/**
> +  Generate init-vector for AES encryption.
> +
> +  @param[out]   InitVector  IVEC buffer.
> +  @param[in]    Size        Size of IVEC requested.
> +
> +  @retval TRUE    IVEC was generated successfully.
> +  @retval FALSE   Failed to generate IVEC.
> +
> +**/
> +STATIC
> +BOOLEAN
> +EncVarLibGenIvec (
> +  OUT UINT8  *InitVector,
> +  IN  UINTN  Size
> +  )
> +{
> +  return RandomBytes (InitVector, Size);
> +}
> +
> +/**
> +  Check if there's valid variable information needed by encrypting or decrypting.
> +
> +  @param[in]    VarEncInfo    Buffer conveying details about a variable.
> +  @param[in]    CheckForEnc   Flag indicating check for encrypting (TRUE) or
> +                              decrypting (FALSE).
> +
> +  @retval TRUE    VarEncInfo is valid.
> +  @retval FALSE   VarEncInfo is invalid.
> +
> +**/
> +STATIC
> +BOOLEAN
> +IsValidVariableInfo (
> +  IN VARIABLE_ENCRYPTION_INFO  *VarEncInfo,
> +  IN BOOLEAN                   CheckForEnc
> +  )
> +{
> +  BOOLEAN  Valid;
> +
> +  if (CheckForEnc) {
> +    Valid = (VarEncInfo->Header.Data != NULL && VarEncInfo->Header.DataSize >
> 0)
> +            || (VarEncInfo->PlainData != NULL && VarEncInfo->PlainDataSize > 0);
> +    if (!Valid) {
> +      ASSERT (
> +        (VarEncInfo->Header.Data != NULL && VarEncInfo->Header.DataSize > 0)
> +             || (VarEncInfo->PlainData != NULL && VarEncInfo->PlainDataSize > 0)
> +        );
> +    }
> +  } else {
> +    Valid = (VarEncInfo->Header.Data != NULL && VarEncInfo->Header.DataSize >
> 0)
> +            || (VarEncInfo->CipherData != NULL && VarEncInfo->CipherDataSize >
> 0);
> +    if (!Valid) {
> +      ASSERT (
> +        (VarEncInfo->Header.Data != NULL && VarEncInfo->Header.DataSize > 0)
> +             || (VarEncInfo->CipherData != NULL && VarEncInfo->CipherDataSize >
> 0)
> +        );
> +    }
> +  }
> +
> +  Valid = Valid
> +          && VarEncInfo->Header.VariableName != NULL
> +          && VarEncInfo->Header.NameSize > 0
> +          && VarEncInfo->Header.VendorGuid != NULL
> +          && VarEncInfo->Key != NULL
> +          && VarEncInfo->KeySize > 0;
> +  if (!Valid) {
> +    ASSERT (VarEncInfo->Header.VariableName != NULL);
> +    ASSERT (VarEncInfo->Header.NameSize != 0);
> +    ASSERT (VarEncInfo->Header.VendorGuid != NULL);
> +    ASSERT (VarEncInfo->Key != NULL);
> +    ASSERT (VarEncInfo->KeySize > 0);
> +  }
> +
> +  return Valid;
> +}
> +
> +/**
> +  Sanity check of encrption header prefixed to encrypted data.

[JianJW] typo: " encrption" -> "encryption"

> +
> +  @param[in]    EncHeader   Pointer to VARIABLE_ENCRYPTION_HEADER.
> +  @param[in]    DataSize    Size of variable data payload.
> +
> +  @retval TRUE    EncHeader is valid.
> +  @retval FALSE   EncHeader is invalid.
> +
> +**/
> +STATIC
> +BOOLEAN
> +IsValidEncrptionHeader (

[JianJW] "IsValidEncrptionHeader" -> " IsValidEncryptionHeader"

> +  IN VARIABLE_ENCRYPTION_HEADER  *EncHeader,
> +  IN UINT32                      DataSize
> +  )
> +{
> +  if (  (DataSize > sizeof (VARIABLE_ENCRYPTION_HEADER))
> +     && ((EncHeader->DataType == ENC_TYPE_AES) || (EncHeader->DataType
> == ENC_TYPE_NULL))
> +     && (EncHeader->HeaderSize >= sizeof (VARIABLE_ENCRYPTION_HEADER))
> +     && (EncHeader->CipherDataSize > 0)
> +     && ((EncHeader->CipherDataSize % ENC_BLOCK_SIZE) == 0)
> +     && (EncHeader->PlainDataSize > 0)
> +     && (EncHeader->PlainDataSize <= EncHeader->CipherDataSize)
> +     && ((EncHeader->CipherDataSize + EncHeader->HeaderSize) <= DataSize))
> +  {
> +    return TRUE;
> +  }
> +
> +  return FALSE;
> +}
> +
> +/**
> +  Encrypt variable data.
> +
> +  If VarEncInfo->PlainData is not NULL, VarEncInfo->PlainData holds the plain
> +  data. Otherwise, VarEncInfo->Headr.Data is supposed to be the plain data.

[JianJW] "Headr" -> "Header"

> +
> +  If VarEncInfo->CipherData is not NULL, The encrypted data is stored in
> +  VarEncInfo->CipherData. Otherwise, the encrypted data is stored directly
> +  in variable data buffer, i.e. VarEncInfo->Headr.Data.

[JianJW] "Headr" -> "Header"

> +
> +  @param[in, out]   VarEncInfo   Pointer to structure containing detailed
> +                                 information about a variable.
> +
> +  @retval EFI_SUCCESS             Variable was encrypted successfully.
> +  @retval EFI_INVALID_PARAMETER   Variable information in VarEncInfo is
> invalid.
> +  @retval EFI_BUFFER_TOO_SMALL    VarEncInfo->CipherData is not NULL but
> +                                  VarEncInfo->CipherDataSize is too small.
> +  @retval EFI_ABORTED             Uknown error occurred during encrypting.
> +  @retval EFI_OUT_OF_RESOURCES    Fail to allocate enough resource.
> +  @retval EFI_UNSUPPORTED         Unsupported to encrypt variable.
> +
> +**/
> +EFI_STATUS
> +EFIAPI
> +EncryptVariable (
> +  IN OUT VARIABLE_ENCRYPTION_INFO  *VarEncInfo
> +  )
> +{
> +  EFI_STATUS                  Status;
> +  VOID                        *AesContext;
> +  UINT8                       EncKey[ENC_KEY_SIZE];
> +  UINT8                       Ivec[ENC_IVEC_SIZE];
> +  UINT8                       *PlainBuffer;
> +  UINT8                       *CipherBuffer;
> +  UINT8                       *PlainData;
> +  UINT32                      PlainDataSize;
> +  VARIABLE_ENCRYPTION_HEADER  *CipherData;
> +  UINT32                      CipherDataSize;
> +  UINT32                      PaddingBytes;
> +
> +  Status       = EFI_ABORTED;
> +  AesContext   = NULL;
> +  PlainBuffer  = NULL;
> +  CipherBuffer = NULL;
> +
> +  if (!IsValidVariableInfo (VarEncInfo, TRUE)) {
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  if (VarEncInfo->PlainData != NULL) {
> +    PlainData     = VarEncInfo->PlainData;
> +    PlainDataSize = VarEncInfo->PlainDataSize;
> +  } else {
> +    PlainData     = VarEncInfo->Header.Data;
> +    PlainDataSize = (UINT32)VarEncInfo->Header.DataSize;
> +  }
> +
> +  CipherDataSize = AES_CIPHER_DATA_SIZE (PlainDataSize);
> +  if (VarEncInfo->CipherData != NULL) {
> +    if (VarEncInfo->CipherDataSize
> +        < (CipherDataSize + sizeof (VARIABLE_ENCRYPTION_HEADER)))
> +    {
> +      VarEncInfo->CipherDataSize = CipherDataSize
> +                                   + sizeof (VARIABLE_ENCRYPTION_HEADER);
> +      return EFI_BUFFER_TOO_SMALL;
> +    }
> +
> +    CipherData = VarEncInfo->CipherData;
> +  } else {
> +    CipherData = VarEncInfo->Header.Data;
> +  }
> +
> +  //
> +  // Prepare buffer for encrypted data.
> +  //
> +  if ((UINTN)CipherData == (UINTN)PlainData) {
> +    //
> +    // Need buffer to store the encrypted data temporarily.
> +    //
> +    CipherBuffer = (UINT8 *)AllocateZeroPool (
> +                              CipherDataSize
> +                              + sizeof (VARIABLE_ENCRYPTION_HEADER)
> +                              );
> +    if (CipherBuffer == NULL) {
> +      ASSERT (CipherBuffer != NULL);
> +      return EFI_OUT_OF_RESOURCES;
> +    }
> +  } else {
> +    CipherBuffer = (UINT8 *)CipherData;
> +  }
> +
> +  //
> +  // Plain variable data must also be multiple of ENC_BLOCK_SIZE.
> +  //
> +  PaddingBytes = ALIGN_VALUE (PlainDataSize, ENC_BLOCK_SIZE) -
> PlainDataSize;
> +  if (PaddingBytes != 0) {
> +    //
> +    // Since the plain data size will be saved in the
> VARIABLE_ENCRYPTION_HEADER,
> +    // there's no need to do PKCS way of padding. To save space, just padding
> +    // the plain data to be of the nearest n*ENC_BLOCK_SIZE.
> +    //
> +    PlainBuffer = AllocateZeroPool (PlainDataSize + PaddingBytes);
> +    if (PlainBuffer == NULL) {
> +      ASSERT (PlainBuffer != NULL);
> +      goto Done;
> +    }
> +
> +    CopyMem (PlainBuffer, PlainData, PlainDataSize);
> +    SetMem (PlainBuffer + PlainDataSize, PaddingBytes, ENC_PADDING_BYTE);
> +  } else {
> +    PlainBuffer = PlainData;
> +  }
> +
> +  //
> +  // Skip EFI_VARIABLE_APPEND_WRITE bit in generating encryption key.
> +  //
> +  VarEncInfo->Header.Attributes &= (~EFI_VARIABLE_APPEND_WRITE);
> +  if (!EncVarLibGenEncKey (VarEncInfo, ENC_KEY_SIZE, EncKey)) {
> +    ASSERT (FALSE);
> +    return EFI_ABORTED;
> +  }
> +
> +  if (!EncVarLibGenIvec (Ivec, ENC_IVEC_SIZE)) {
> +    ASSERT (FALSE);
> +    return EFI_ABORTED;
> +  }
> +
> +  AesContext = AllocateZeroPool (AesGetContextSize ());
> +  if (AesContext == NULL) {
> +    ASSERT (AesContext != NULL);
> +    return EFI_OUT_OF_RESOURCES;
> +  }
> +
> +  if (!AesInit (AesContext, EncKey, ENC_KEY_SIZE * 8)) {
> +    ASSERT (FALSE);
> +    goto Done;
> +  }
> +
> +  if (AesCbcEncrypt (
> +        AesContext,
> +        PlainBuffer,
> +        PlainDataSize + PaddingBytes,
> +        Ivec,
> +        CipherBuffer + sizeof (VARIABLE_ENCRYPTION_HEADER)
> +        ))
> +  {
> +    //
> +    // Keep the IV for decryption.
> +    //
> +    CopyMem (CipherData->KeyIvec, Ivec, ENC_BLOCK_SIZE);
> +
> +    if ((UINTN)CipherBuffer != (UINTN)CipherData) {
> +      CopyMem (
> +        CipherData + 1,
> +        CipherBuffer + sizeof (VARIABLE_ENCRYPTION_HEADER),
> +        CipherDataSize
> +        );
> +    }
> +
> +    CipherData->CipherDataSize = CipherDataSize;
> +    CipherData->PlainDataSize  = PlainDataSize;
> +    CipherData->DataType       = ENC_TYPE_AES;
> +    CipherData->HeaderSize     = sizeof (VARIABLE_ENCRYPTION_HEADER);
> +
> +    VarEncInfo->CipherData       = CipherData;
> +    VarEncInfo->CipherDataSize   = CipherDataSize + sizeof
> (VARIABLE_ENCRYPTION_HEADER);
> +    VarEncInfo->CipherHeaderSize = sizeof (VARIABLE_ENCRYPTION_HEADER);
> +    VarEncInfo->CipherDataType   = ENC_TYPE_AES;
> +
> +    Status = EFI_SUCCESS;
> +  } else {
> +    VarEncInfo->CipherData       = NULL;
> +    VarEncInfo->CipherDataSize   = 0;
> +    VarEncInfo->CipherHeaderSize = 0;
> +    VarEncInfo->CipherDataType   = ENC_TYPE_NULL;
> +
> +    ASSERT (FALSE);
> +  }
> +
> +Done:
> +  FREE_POOL (AesContext);
> +  if (PlainBuffer != PlainData) {
> +    FREE_POOL (PlainBuffer);
> +  }
> +
> +  if (CipherBuffer != (UINT8 *)CipherData) {
> +    FREE_POOL (CipherBuffer);
> +  }
> +
> +  return Status;
> +}
> +
> +/**
> +  Decrypt variable data.
> +
> +  If VarEncInfo->CipherData is not NULL, it must holds the cipher data to be
> +  decrypted. Otherwise, assume the cipher data from variable data buffer, i.e.
> +  VarEncInfo->Header.Data.
> +
> +  If VarEncInfo->Flags.DecryptInPlace is TRUE, the decrypted data will be put
> +  back in the same buffer as cipher buffer got above, after encryption header,
> +  which helps to identify later if the data in buffer is decrypted or not. This
> +  can avoid repeat decryption when accessing the same variable more than
> once.
> +
> +  If VarEncInfo->Flags.DecryptInPlace is FALSE, VarEncInfo->PlainData must be
> +  passed in with a valid buffer with VarEncInfo->PlainDataSize set correctly
> +  with its size.
> +
> +  Note the VarEncInfo->PlainData is always pointing to the buffer address with
> +  decrypted data without encryption header, and VarEncInfo->PlainDataSize is
> +  always the size of original variable data, if this function returned
> +  successfully.
> +
> +  @param[in, out]   VarEncInfo   Pointer to structure containing detailed
> +                                 information about a variable.
> +
> +  @retval EFI_SUCCESS             Variable was decrypted successfully.
> +  @retval EFI_INVALID_PARAMETER   Variable information in VarEncInfo is
> invalid.
> +  @retval EFI_BUFFER_TOO_SMALL    VarEncInfo->PlainData is not NULL but
> +                                  VarEncInfo->PlainDataSize is too small.
> +  @retval EFI_ABORTED             Uknown error occurred during decrypting.
> +  @retval EFI_OUT_OF_RESOURCES    Fail to allocate enough resource.
> +  @retval EFI_COMPROMISED_DATA    The cipher header is not valid.
> +  @retval EFI_UNSUPPORTED         Unsupported to encrypt variable.
> +
> +**/
> +EFI_STATUS
> +EFIAPI
> +DecryptVariable (
> +  IN OUT VARIABLE_ENCRYPTION_INFO  *VarEncInfo
> +  )
> +{
> +  VOID                        *AesContext;
> +  UINT8                       EncKey[ENC_KEY_SIZE];
> +  UINT8                       *PlainBuffer;
> +  UINT8                       *PlainData;
> +  VARIABLE_ENCRYPTION_HEADER  *CipherData;
> +  UINT32                      CipherDataSize;
> +  EFI_STATUS                  Status;
> +
> +  Status      = EFI_ABORTED;
> +  AesContext  = NULL;
> +  PlainBuffer = NULL;
> +
> +  if (!IsValidVariableInfo (VarEncInfo, FALSE)) {
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  if (VarEncInfo->CipherData != NULL) {
> +    CipherData     = VarEncInfo->CipherData;
> +    CipherDataSize = VarEncInfo->CipherDataSize;
> +  } else {
> +    CipherData     = VarEncInfo->Header.Data;
> +    CipherDataSize = (UINT32)VarEncInfo->Header.DataSize;
> +  }
> +
> +  //
> +  // Sanity check of cipher header.
> +  //
> +  if (!IsValidEncrptionHeader (CipherData, CipherDataSize)) {
> +    return EFI_COMPROMISED_DATA;
> +  }
> +
> +  if (  (VarEncInfo->PlainData != NULL)
> +     && (VarEncInfo->PlainDataSize < CipherData->PlainDataSize))
> +  {
> +    VarEncInfo->PlainDataSize = CipherData->PlainDataSize;
> +    return EFI_BUFFER_TOO_SMALL;
> +  }
> +
> +  if (CipherData->DataType == ENC_TYPE_AES) {
> +    if (VarEncInfo->Flags.DecryptInPlace) {
> +      //
> +      // Reusing cipher data buffer needs to keep the encryption header.
> +      //
> +      PlainData = (UINT8 *)CipherData + CipherData->HeaderSize;
> +    } else {
> +      PlainData = VarEncInfo->PlainData;
> +    }
> +
> +    if (PlainData == NULL) {
> +      return EFI_INVALID_PARAMETER;
> +    }
> +
> +    //
> +    // Always need buffer to store the decrypted data temporarily, due to
> +    // padding bytes or buffer reuse. Then the buffer must be larger than
> +    // CipherData->PlainDataSize.
> +    //
> +    PlainBuffer = AllocatePages (EFI_SIZE_TO_PAGES (CipherDataSize));
> +    if (PlainBuffer == NULL) {
> +      ASSERT (PlainBuffer != NULL);
> +      return EFI_OUT_OF_RESOURCES;
> +    }
> +
> +    if (!EncVarLibGenEncKey (VarEncInfo, ENC_KEY_SIZE, EncKey)) {
> +      ASSERT (FALSE);
> +      goto Done;
> +    }
> +
> +    AesContext = AllocatePages (EFI_SIZE_TO_PAGES (AesGetContextSize ()));
> +    if (AesContext == NULL) {
> +      ASSERT (AesContext != NULL);
> +      Status = EFI_OUT_OF_RESOURCES;
> +      goto Done;
> +    }
> +
> +    if (!AesInit (AesContext, EncKey, ENC_KEY_SIZE * 8)) {
> +      ASSERT (FALSE);
> +      goto Done;
> +    }
> +
> +    if (AesCbcDecrypt (
> +          AesContext,
> +          (UINT8 *)CipherData + CipherData->HeaderSize,
> +          CipherDataSize - CipherData->HeaderSize,
> +          CipherData->KeyIvec,
> +          PlainBuffer
> +          ))
> +    {
> +      Status = EFI_SUCCESS;
> +    } else {
> +      Status = EFI_COMPROMISED_DATA;
> +    }
> +  } else {
> +    //
> +    // The data has been decrypted already.
> +    //
> +    PlainBuffer = (UINT8 *)CipherData + CipherData->HeaderSize;
> +
> +    if (VarEncInfo->PlainData != NULL) {
> +      PlainData = VarEncInfo->PlainData;
> +    } else {
> +      PlainData = PlainBuffer;
> +    }
> +
> +    Status = EFI_SUCCESS;
> +  }
> +
> +  if (!EFI_ERROR (Status)) {
> +    if (PlainBuffer != PlainData) {
> +      CopyMem (PlainData, PlainBuffer, CipherData->PlainDataSize);
> +    }
> +
> +    if (VarEncInfo->PlainData != NULL) {
> +      if (VarEncInfo->PlainData != PlainBuffer) {
> +        CopyMem (VarEncInfo->PlainData, PlainBuffer, CipherData-
> >PlainDataSize);
> +      }
> +    } else {
> +      VarEncInfo->PlainData = PlainData;
> +    }
> +
> +    VarEncInfo->PlainDataSize    = CipherData->PlainDataSize;
> +    VarEncInfo->CipherHeaderSize = CipherData->HeaderSize;
> +    VarEncInfo->CipherDataType   = CipherData->DataType;
> +
> +    if (VarEncInfo->Flags.DecryptInPlace) {
> +      CipherData->DataType = ENC_TYPE_NULL;
> +    }
> +  }
> +
> +Done:
> +  if (AesContext != NULL) {
> +    FreePages (AesContext, EFI_SIZE_TO_PAGES (AesGetContextSize ()));
> +  }
> +
> +  if (PlainBuffer != NULL) {
> +    FreePages (PlainBuffer, EFI_SIZE_TO_PAGES ((CipherDataSize)));
> +  }
> +
> +  return Status;
> +}
> +
> +/**
> +  Get cipher information about a variable, including plaindata size,
> +  cipher algorithm type, etc.
> +
> +  For data passed in with VarEncInfo,
> +
> +    VarEncInfo->Header.Data
> +      - The variable data in normal variable structure.
> +    VarEncInfo->Header.DataSize
> +      - The size of variable data.
> +
> +  For data passed out with VarEncInfo (valid only if EFI_SUCCESS is returned),
> +
> +    VarEncInfo->CipherDataType
> +      - ENC_TYPE_NULL, if the variable is not encrypted or has been decrypted;
> +      - ENC_TYPE_AES, if the variable is encrypted.
> +    VarEncInfo->CipherHeaderSize
> +      - Size of cipher header put before encrypted or decrypted data.
> +    VarEncInfo->PlainData
> +      - NULL, if the variable is encrypted; Or
> +      - pointer to original variable data, if the variable has been decrypted.
> +    VarEncInfo->PlainDataSize
> +      - The size of original variable data
> +    VarEncInfo->CipherData
> +      - NULL, if the variable is decrypted; Or
> +      - pointer to start of encrypted variable data, including encryption header;
> +    VarEncInfo->CipherDataSize
> +      - The size of encrypted variable data, including encryption header.
> +
> +  @param[in]   VarEncInfo   Pointer to structure containing detailed
> +                            information about a variable.
> +
> +  @retval EFI_SUCCESS             The information was retrieved successfully.
> +  @retval EFI_INVALID_PARAMETER   Variable information in VarEncInfo is
> invalid.
> +  @retval EFI_NOT_FOUND           No cipher information recognized.
> +  @retval EFI_UNSUPPORTED         Unsupported interface.
> +
> +**/
> +EFI_STATUS
> +EFIAPI
> +GetCipherDataInfo (
> +  IN VARIABLE_ENCRYPTION_INFO  *VarEncInfo
> +  )
> +{
> +  VARIABLE_ENCRYPTION_HEADER  *EncHeader;
> +
> +  if ((VarEncInfo->Header.Data == NULL) || (VarEncInfo->Header.DataSize == 0))
> {
> +    ASSERT (VarEncInfo->Header.Data != NULL);
> +    ASSERT (VarEncInfo->Header.DataSize != 0);
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  //
> +  // Validate encryption header.
> +  //
> +  EncHeader = (VARIABLE_ENCRYPTION_HEADER *)VarEncInfo->Header.Data;
> +  if (!IsValidEncrptionHeader (EncHeader, (UINT32)VarEncInfo-
> >Header.DataSize)) {
> +    //
> +    // Not an encrypted variable.
> +    //
> +    return EFI_NOT_FOUND;
> +  }
> +
> +  if (EncHeader->DataType == ENC_TYPE_NULL) {
> +    //
> +    // The data must have been decrypted.
> +    //
> +    VarEncInfo->PlainData            = (UINT8 *)VarEncInfo->Header.Data +
> EncHeader->HeaderSize;
> +    VarEncInfo->CipherData           = NULL;
> +    VarEncInfo->Flags.DecryptInPlace = TRUE;
> +  } else {
> +    //
> +    // The data is encrypted.
> +    //
> +    VarEncInfo->CipherData           = VarEncInfo->Header.Data;
> +    VarEncInfo->PlainData            = NULL;
> +    VarEncInfo->Flags.DecryptInPlace = FALSE;
> +  }
> +
> +  VarEncInfo->PlainDataSize    = EncHeader->PlainDataSize;
> +  VarEncInfo->CipherDataSize   = EncHeader->CipherDataSize + EncHeader-
> >HeaderSize;
> +  VarEncInfo->CipherDataType   = EncHeader->DataType;
> +  VarEncInfo->CipherHeaderSize = EncHeader->HeaderSize;
> +
> +  return EFI_SUCCESS;
> +}
> +
> +/**
> +  Force set cipher information for a variable, like plaindata size,
> +  cipher algorithm type, cipher data etc.
> +
> +  The destination buffer must be passed via VarEncInfo->Header.Data.
> +
> +  This method is only used to update and/or change plain data information.
> +
> +  @param[in]   VarEncInfo   Pointer to structure containing detailed
> +                            information about a variable.
> +
> +  @retval EFI_SUCCESS             The information was updated successfully.
> +  @retval EFI_INVALID_PARAMETER   Variable information in VarEncInfo is
> invalid.
> +  @retval EFI_UNSUPPORTED         If this method is not supported.
> +
> +**/
> +EFI_STATUS
> +EFIAPI
> +SetCipherDataInfo (
> +  IN VARIABLE_ENCRYPTION_INFO  *VarEncInfo
> +  )
> +{
> +  VARIABLE_ENCRYPTION_HEADER  *EncHeader;
> +  UINT8                       *Data;
> +
> +  if (  (VarEncInfo->Header.Data == NULL)
> +     || (VarEncInfo->Header.DataSize < sizeof
> (VARIABLE_ENCRYPTION_HEADER))
> +     || (VarEncInfo->CipherDataType != ENC_TYPE_NULL))
> +  {
> +    ASSERT (VarEncInfo->Header.Data != NULL);
> +    ASSERT (VarEncInfo->Header.DataSize >= sizeof
> (VARIABLE_ENCRYPTION_HEADER));
> +    ASSERT (VarEncInfo->CipherDataType == ENC_TYPE_NULL);
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  Data      = VarEncInfo->Header.Data;
> +  EncHeader = (VARIABLE_ENCRYPTION_HEADER *)Data;
> +
> +  if (  !IsValidEncrptionHeader (EncHeader, (UINT32)VarEncInfo-
> >Header.DataSize)
> +     || (VarEncInfo->PlainDataSize > EncHeader->CipherDataSize))
> +  {
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  if ((VarEncInfo->PlainData != NULL) && (VarEncInfo->PlainDataSize > 0)) {
> +    CopyMem (
> +      Data + EncHeader->HeaderSize,
> +      VarEncInfo->PlainData,
> +      VarEncInfo->PlainDataSize
> +      );
> +  }
> +
> +  EncHeader->DataType = VarEncInfo->CipherDataType;
> +  if (VarEncInfo->PlainDataSize != 0) {
> +    EncHeader->PlainDataSize = VarEncInfo->PlainDataSize;
> +  }
> +
> +  return EFI_SUCCESS;
> +}
> --
> 2.35.1.windows.2